1. Field of the Invention
The present invention relates generally to laser scanning systems, and more particularly to an automatic bar code symbol reading system having an automatic hand-supportable laser scanner which can be utilized in diverse lighting environments with natural hand movements, while conserving electrical power.
2. Brief Description of the Prior Art
Bar code symbols have become widely used in many commercial environments such as, for example, point-of-sale (pos) stations in retail stores and supermarkets, inventory and document tracking, and diverse data control applications.
To meet the growing demands of this recent innovation, bar code symbol readers of various types have been developed for scanning and decoding bar code symbol patterns. Typically, the symbol character data produced from such bar code readers is provided as input to automated data processing systems.
In general, prior art hand-held bar code symbol readers using laser scanning mechanisms can be classified into three categories.
The first category of hand-held bar code symbol readers includes systems having manually-actuated laser scanners which can be supported in the hand of the user. The user positions the hand-held laser scanner at a specified distance from the object bearing the bar code symbol, manually activates the scanner to initiate reading (e.g. by pulling a trigger), and then moves the scanner over other objects bearing bar code symbols to be read. Prior art bar code symbol readers illustrative of this first category are disclosed in U.S. Pat. Nos. 4,387,297 to Swartz; 4,575,625 to Knowles; 4,639,606 to Boles et al., 4,845,349 to Cherry; 4,825,057 to Swartz, et al.; 4,903,848 to Knowles; 4,933,538 to Heiman, et al.; 5,107,100 to Shepard, et al.; 5,080,456 to Katz, et al.; and 5,047,617 to Shepard et al.
The second category of hand-held bar code symbol readers includes systems utilizing hand-held scanners which have (i) a tungsten bulb, a Xenon lamp, or light emitting diodes (LEDs) to radiate light onto a bar code symbol, and (ii) an electronically scanned image sensor (e.g. CCD array) for converting the image of light reflected off the bar code symbol into a corresponding signal for decode processing. Exemplary systems of this type are disclosed in U.S. Pat. Nos. 4,570,057 to Chadima, et al., 4,818,847 to Hara, et al and 4,877,949 to Danielson, et al.
The third category of hand-held bar code symbol readers includes systems utilizing fully automated hand-held laser scanners having intelligent programs which control the operation device under diverse user operating conditions. Exemplary systems of this type of bar code symbol reading technology are disclosed in pending U.S. application Ser. Nos. 07/898,919 and 07/761,123.
While prior art hand-held manually triggered and CCD type scanners have played an important role in the development of the bar code symbol industry, these devices, suffer from a number of shortcomings and drawbacks. For example, hand-held manually-actuated laser scanners, although portable and lightweight, are not always convenient to use particularly in applications where the user must read bar coded objects over an extended period of time. In many applications, where bar coded objects to be identified reside at arms length from the user's reach, hand-held CCD scanners are difficult to operate owing to their limited depth of field.
Unlike manually automated hand-held bar code scanners, fully automatic hand-held laser scanners do not cause fatigue due to their automatic operation. Also, owing to their extended depth of field, automatic hand-held laser scanners provide increased flexibility by allowing the user to read bar coded objects residing at distances of six or more inches away from the scanner. However, even though automatic hand-held laser bar code scanners offer superior performance in most scanning applications, it has been found that in intensely illuminated scanning environments, the user's ability to perceive the visible laser scanning beam is significantly diminished in the scan field of the device. Consequently, in such scanning environments, it is difficult to visually align (i.e. register) the laser scanning beam with the bar code symbol to be scanned, thus hindering the automatic bar code symbol reading process. While the use of a higher power visible laser beam might render the beam more easily perceptible, this approach is undesirable for laser safety and power consumption reasons.
Thus, there is a great need in the bar code symbol reading art for a hand-supportable laser bar code symbol reading system which overcomes the above described shortcomings and drawbacks of prior art devices and techniques, while permitting use over a diverse range of laser scanning environments.